Supplemental Financial Information - Summary of Depreciation, Amortization, Accretion and Depletion (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				$ 3,477	$ 2,227	$ 2,080
Regulatory assets				407	170	191
Amortization of Intangible Assets				87	76	179
Nuclear fuel	[1]			1,159	1,116	1,073
ARO accretion	[2]			446	398	345
Total depreciation, amortization and accretion				5,576	3,987	3,868
Exelon Generation Co L L C [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				1,835	1,007	922
Regulatory assets				0	0	0
Amortization of Intangible Assets				79	69	179
Nuclear fuel	[1]			1,159	1,116	1,073
ARO accretion	[2]			446	397	345
Total depreciation, amortization and accretion				3,519	2,589	2,519
Commonwealth Edison Co [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				708	635	588
Regulatory assets				67	72	99
Amortization of Intangible Assets				7	7	7
Nuclear fuel	[1]			0	0	0
ARO accretion	[2]			0	0	0
Total depreciation, amortization and accretion				775	707	687
PECO Energy Co [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				244	240	227
Regulatory assets				26	20	9
Nuclear fuel	[1]			0	0	0
ARO accretion	[2]			0	0	0
Total depreciation, amortization and accretion				270	260	236
Baltimore Gas and Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				299	289	288
Regulatory assets				124	77	83
Nuclear fuel	[1]			0	0	0
ARO accretion	[2]			0	0	0
Total depreciation, amortization and accretion				423	366	371
Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment			$ 325
Regulatory assets			190
Nuclear fuel	[1]		0
ARO accretion	[2]		0
Total depreciation, amortization and accretion			515
Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment		$ 94
Regulatory assets		58
Nuclear fuel	[1]	0
ARO accretion	[2]	0
Total depreciation, amortization and accretion		152			624	526
Potomac Electric Power Company [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				175	164	155
Regulatory assets				120	92	57
Nuclear fuel	[1]			0	0	0
ARO accretion	[2]			0	0	0
Total depreciation, amortization and accretion				295	256	212
Potomac Electric Power Company [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment					392	363
Regulatory assets					232	163
Nuclear fuel	[1]				0	0
ARO accretion	[2]				0	0
Delmarva Power and Light Company [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				110	103	94
Regulatory assets				47	45	28
Nuclear fuel	[1]			0	0	0
ARO accretion	[2]			0	0	0
Total depreciation, amortization and accretion				157	148	122
Atlantic City Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				82
Regulatory assets				83
Nuclear fuel	[1]			0
ARO accretion	[2]			0
Total depreciation, amortization and accretion				165	175	155
Atlantic City Electric Company [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment					76	72
Regulatory assets					99	83
Nuclear fuel	[1]				0	0
ARO accretion	[2]				0	0
Unamortized Energy Contracts [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			35	22	135
Unamortized Energy Contracts [Member] | Exelon Generation Co L L C [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			35	22	135
Unamortized Energy Contracts [Member] | Commonwealth Edison Co [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			0	0	0
Unamortized Energy Contracts [Member] | PECO Energy Co [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			0	0	0
Unamortized Energy Contracts [Member] | Baltimore Gas and Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			0	0	0
Unamortized Energy Contracts [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]		0
Unamortized Energy Contracts [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]	0
Unamortized Energy Contracts [Member] | Potomac Electric Power Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			0	0	0
Unamortized Energy Contracts [Member] | Potomac Electric Power Company [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]				0	0
Unamortized Energy Contracts [Member] | Delmarva Power and Light Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			0	0	0
Unamortized Energy Contracts [Member] | Atlantic City Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			0
Unamortized Energy Contracts [Member] | Atlantic City Electric Company [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]				0	0
Other Intangible Assets [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				52	54	44
Other Intangible Assets [Member] | Exelon Generation Co L L C [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				44	47	44
Other Intangible Assets [Member] | Commonwealth Edison Co [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				0	0	0
Other Intangible Assets [Member] | PECO Energy Co [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				0	0	0
Other Intangible Assets [Member] | Baltimore Gas and Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				0	0	0
Other Intangible Assets [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets			$ 0
Other Intangible Assets [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets		$ 0
Other Intangible Assets [Member] | Potomac Electric Power Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				0	0	0
Other Intangible Assets [Member] | Potomac Electric Power Company [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets					0	0
Other Intangible Assets [Member] | Delmarva Power and Light Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				0	0	0
Other Intangible Assets [Member] | Atlantic City Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				$ 0
Other Intangible Assets [Member] | Atlantic City Electric Company [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets					$ 0	$ 0

[1] Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.

[2] Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.

[3] Included in Operating revenues or Purchased power and fuel on the Registrants’ Consolidated Statements of Operations and Comprehensive Income